'Blue Screen Walking Etc' The file contains correspondence, brochures, lists and photographs concerning the provision of a rig for blue screen tracking, a special effects process whereby actors work in front of a blue or green background, which is replaced in post-production with other footage or computer-generated images to form a single image. Included is a table comparing cine and Single Lens Reflex (SLR) cameras with details of focal lengths and fields of view, a camera cranes brochure and sketches for a blue screen rig set-up with estimated costs and pictures of one. 1996